Magnetic susceptibility patterns and provenance of ice-rafted material at Feni Drift, Rockall Trough: implications for the history of the British-Irish ice sheet

Piston core ENAM 97-09 from Feni Drift, Atlantic margin west of Ireland pro vides a record of IRD input variability and provenance during the last simi lar to 250,000 yrs. The IRD patterns can be related to Late Devensian (<30, 000 yrs BP) ice advances and retreats at the southwestern sector of the Bri tish-Irish ice sheet (BIIS) known from terrestrial investigations, Inferenc es can be made about the BIIS evolution during earlier periods, which is po orly constrained from the land record. Detrital carbonate and (meta)sedimen tary rock fragments represent two major IRD types, which were dominantly de rived from Irish inland ice and the Irish Sea ice stream, respectively: add itional evidence fur the latter source is based on heavy mineral data. Inpu t from other circum-North Atlantic ice sheets, notably the Laurentide ice s heet, is minor compared to British-Irish IRD, at least during periods of ma ximum expansion of the BIIS. This is consistent with the marginal location of the core site with reference to the: main North Atlantic IRD belt. On th e: other hand, Laurentide IRD presumably accounts for minor IRD peaks at ti mes of reduced ice volume in the British Isles, The main magnetic susceptib ility peak during late isotope stage 2/Termination I can be related to IRD input from the Laurentide ice sheet. following early decay of the BIIS. A s imilar pattern is observed during oxygen isotope stage 6. These observation s are consistent with recent provenance studies indicating that only Lauren tide IRD carries a strong magnetic susceptibility signal, (C) 2001 Elsevier Science B.V. All rights reserved.